I see something that sucks, a process, education, something that could be better, faster cheaper through the use of computers and I want to improve it. I can't help it I want to improve it, being part of the "solution" not the "problem". "Make the world a little better" through the use of software. A startup allows me to keep doing that, while paying for my expenses in order to sustain my life. And hopefully if I create enough value, and with a little luck generate enough money so that I don't need to worry too much about the means to sustain my life and then find something else worth improving.